The present invention relates to high efficiency gaseous electric discharge lamps, and, more particularly, to such lamps which emit light in a plurality of distinct narrow spectral lines.
The desire for increased street lighting, well lighted parking lots, and lighted freeways has increased the sky glow of the night sky due to reflected light and light which is directed upward away from the street lighting fixtures. This creates particular problems in the vicinities around astronomical observatories. As astronomers are developing advanced techniques enabling them to count very low light levels emitted by faint objects in the sky the interference with observation by sky glow has become more pronounced.
One prior art lamp type that effectively satisfies the need for lighting in the vicinity of observatories without interfering significantly with observational techniques is the low pressure sodium lamp, because it is a narrow-lined source. This narrow-lined source can be filtered or ignored in the astronomical observations. While low pressure sodium lamps satisfy astronomers needs, they are not generally satisfactory for other inhabitants of the community. The light emitted by low pressure sodium lamps is a yellow monochromatic light which causes most objects to appear in unnatural colors and is very unappealing to many people. A lamp is needed which satisfies the need of the astronomers for an easily filtered source and the desire of residents for adequate, white light.